This invention relates to a brushless d.c. motor, and particularly to a core polyphase coil motor.
Burshless d.c. motors comprise a stator having a stator core with a plurality of pole pieces peripherally disposed in parallel, a stator winding wound around the pole pieces, a pattern conductor for frequency generation and a control circuit for controlling an exciting current of the stator winding responsive to a speed control signal from the pattern conductor, and a rotor rotatably mounted to the stator, having a plurality of permanent magnets opposite to the pole piece surfaces of the stator and a permanent magnet for frequency generation. The pole pieces of the stator core consist of a plurality of linear type pole pieces on which are wound 2-phase coils the phases of which are alternately shifted by 90 degrees. The first phase coils are serially connected so that the polarily alternately changes, each coil being wound over half the roughly root side of two radial pole pieces contiguous to each other. The second phase coils are serially connected, also so that the polarity alternately changes, each coil being wound over half the roughly point side of two pole pieces contiguous to each other, but the pole pieces which are wound by the second coils are shifted by one pole in comparison with the first phase coils. Accordingly, although spaces are formed to receive both coils on the sides of each pole piece which is radially extended, only the outer sides or half the inner sides of these spaces are used to receive the coils. So the remaining half space is not used, and the larger the space for receiving the coils becomes, the greater the unused space becomes. This results in the coils being larger in proportion thereto and the height of the coil end part and the length of the coil strands become greater so that this prior art has the disadvantage that miniturization of the motor, reduction of the d.c. resistance of the coils, and the coil winding operation are all difficult.